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Oisin J. O’Connell, MD, BMedSc; AnneMarie McGarrigle, PhD; Owen J. O’Connor, MD; Michael M. Maher, MD; Barry J. Plant, MD
Author and Funding Information

From Cork Cystic Fibrosis Center (Drs O’Connell and Plant), the Department of Radiation Physics (Dr McGarrigle), and the Department of Radiology (Drs O’Connor and Maher), Cork University Hospital, University College Cork.

Correspondence to: Barry J. Plant, MD, Cork Adult Cystic Fibrosis Center, Cork University Hospital, Cork, Ireland; e-mail: barry.plant@hse.ie


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2012;142(4):1078. doi:10.1378/chest.12-1720
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To the Editor:

We thank Drs de Jong and Owens for their interest in our study published in CHEST1 and agree with their point that all CT scanning must be justified and optimized. Indeed, our study highlights these points in the discussion and explores future strategies to reduce the radiation exposure associated with diagnostic imaging. Furthermore, we agree that the association between radiation exposure in the diagnostic range and the development of cancer remains controversial. However, based on our current understanding and the available evidence, few would argue with the importance of avoiding radiation exposure, if possible, or with obtaining diagnostic imaging examinations at the lowest achievable dose, particularly in children and patient groups with chronic illnesses.

As to whether the doses used in our study for the estimation of cumulative effective dose reflect current practice, we agree that prospectively these doses would not represent the norm. However, we challenge the view that these data are not reflective of retrospective international practice covered in the time period of our study (1992-2009). The estimated effective CT scan doses used in our study were reported by Mettler et al2 in 2008 following analysis of comprehensive data from multiple international centers and were corrected for age using published Monte Carlo correction factors from Imaging Performance Assessment of CT Scanners (ImPACT) for 1-, 5-, 10-, and 15-year-old children.3 Mettler et al’s2 study was used to reflect mean effective doses across a wide range of CT scanners over a time period similar to that used in our study.

We acknowledge the work published by the authors in 2007 on pediatric thoracic CT scanning.4 Our institution also has a specific research program on optimizing CT scanning protocols to reduce radiation exposure in thoracic and abdominal imaging. In 2010, we published our low-dose, thin-slice, thoracic CT scanning protocols for pediatric patients with cystic fibrosis, achieving doses of 0.14 mSv using a four-slice CT scanner.5

The authors’ point on retrospect cumulative effective dose not increasing over the time period studied fails to acknowledge an important finding in our study that demonstrates that >50% of iatrogenic radiation exposure is extrathoracic. Therefore, despite optimizing thoracic CT imaging protocols, there remains a significant issue of extrathoracic radiation exposure, which needs to be addressed. We have also recently developed low-dose submillisievert abdominal CT scanning protocols in this area.6

O’Connell OJ, McWilliams S, McGarrigle AM, et al. Radiologic imaging in cystic fibrosis: cumulative effective dose and changing trends over 2 decades. Chest. 2012;141(6):1575-1583. [PubMed] [CrossRef]
 
Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008;248(1):254-263.
 
ImPACT’s ct dosimetry tool. ImPACT website.http://www.impactscan.org/ctdosimetry.htm. Accessed January 16, 2010.
 
Papaioannou G, Young C, Owens CM. Multidetector row CT for imaging the paediatric tracheobronchial tree. Pediatr Radiol. 2007;37(6):515-529.
 
O’Connor OJ, Vandeleur M, McGarrigle AM, et al. Development of low-dose protocols for thin-section CT assessment of cystic fibrosis in pediatric patients. Radiology. 2010;257(3):820-829.
 
Craig O, O’Neill S, O’Neill F, et al. Diagnostic accuracy of computed tomography using lower doses of radiation for patients with Crohn’s disease. Clin Gastroenterol Hepatol. 2012;10(8):886-892.
 

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References

O’Connell OJ, McWilliams S, McGarrigle AM, et al. Radiologic imaging in cystic fibrosis: cumulative effective dose and changing trends over 2 decades. Chest. 2012;141(6):1575-1583. [PubMed] [CrossRef]
 
Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008;248(1):254-263.
 
ImPACT’s ct dosimetry tool. ImPACT website.http://www.impactscan.org/ctdosimetry.htm. Accessed January 16, 2010.
 
Papaioannou G, Young C, Owens CM. Multidetector row CT for imaging the paediatric tracheobronchial tree. Pediatr Radiol. 2007;37(6):515-529.
 
O’Connor OJ, Vandeleur M, McGarrigle AM, et al. Development of low-dose protocols for thin-section CT assessment of cystic fibrosis in pediatric patients. Radiology. 2010;257(3):820-829.
 
Craig O, O’Neill S, O’Neill F, et al. Diagnostic accuracy of computed tomography using lower doses of radiation for patients with Crohn’s disease. Clin Gastroenterol Hepatol. 2012;10(8):886-892.
 
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